How long does a Challenge last?

There is no time limit. You can take as long as you need to reach your profit target: a Challenge has no expiry date, and there is no penalty for a slow month.

The one deadline that does exist is inactivity. An evaluation account closes if no trade is opened for more than 60 days, and a funded account closes after more than 30 days without a trade. In both cases the account is closed without a refund.

Opening a single position resets the count, so the rule only affects accounts that are left untouched for a long stretch.

Passing quickly is allowed too, as long as you complete the minimum trading days for your plan.